Superdiffusion dominates intracellular particle motion in the supercrowded space of pathogenic Acanthamoeba castellanii

TL;DR

This study reveals that intracellular particles in Acanthamoeba castellanii exhibit superdiffusive motion primarily driven by myosin II motors, with cell locomotion also contributing, highlighting active transport in supercrowded cytoplasm.

Contribution

It demonstrates that superdiffusive intracellular motion in Acanthamoeba is mainly driven by myosin II, providing new insights into active transport mechanisms in supercrowded cellular environments.

Findings

Superdiffusive motion dominates intracellular particle dynamics.

Myosin II is a major driver of active intracellular transport.

Cell locomotion significantly influences particle movement.

Abstract

Acanthamoebae are free-living protists and human pathogens, whose cellular functions and pathogenicity strongly depend on the transport of intracellular vesicles and granules through the cytosol. Using high-speed live cell imaging in combination with single-particle tracking analysis, we show here that the motion of endogenous intracellular particles in the size range from a few hundred nanometers to several micrometers in Acanthamoeba castellanii is strongly superdiffusive and influenced by cell locomotion, cytoskeletal elements, and myosin II. We demonstrate that cell locomotion significantly contributes to intracellular particle motion, but is clearly not the only origin of superdiffusivity. By analyzing the contribution of microtubules, actin, and myosin II motors we show that myosin II is a major driving force of intracellular motion in A. castellanii. The cytoplasm of A. castellanii is supercrowded with intracellular vesicles and granules, such that significant intracellular motion can only be achieved by actively driven motion, while purely thermally driven diffusion is negligible.